Multi-layer barrier preventing wood pest access to wooden structures

ABSTRACT

A method and device are disclosed which prevent the intrusion of insects onto wood structures by using a barrier capable of retaining pesticide. In the disclosed method, the barrier maintains a minimal effective level of insecticide for a predetermined period of time.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 09/030,690filed Feb. 25, 1998, now U.S. Pat. No. 5,985,304.

FIELD OF THE INVENTION

The present invention relates to barriers for preventing wood pest (e.g.termite and boring insect) access to wooden structures for the long-termprotection of wooden structures. More particularly, it relates to acomposition and method which creates and maintains an exclusion zone forinsect pests such as termites, ants and other boring insects. As usedherein, the term “bioactive” means stimulating an organism, usually in anegative way up to and including death for purposes of a deterrent.

BACKGROUND OF THE INVENTION

Wood which is in contact with concrete, such as in wooden buildingconstruction and wood which is in contact with soil for example fenceposts, utility poles, railroad cross-ties and wooden supports, can bestructurally degraded by the action of termites, ants and other boringinsects. Insecticides are available to protect wood from the action ofsuch pests.

In wooden building construction, wood in contact with concrete may bestructurally degraded by action of one or more wood pests including butnot limited to termites, ants and other boring insects. Present methodsof preventing or retarding the advance of insects includes fumigationwherein the entire structure may be sealed and an insecticide releasedtherein. Disadvantages of this method include ecological and humanhealth concerns as well as the limited time until the fumigant issufficiently reduced in concentration to permit insect ingress.

Although insecticides are effective against the action of the boringinsects, the insecticides must be repeatedly applied at intervals offrom a few days to a few months or a year to remain effective. Ifinsecticides are applied by themselves in sufficient quantity to beeffective over a period of time, they pose ecological concerns, humanhealth, and may present unpleasant odors, soil leaching and volatilityof the insecticide. Furthermore, even the greatest amounts ofinsecticides applied by themselves dissipate within a relatively shorttime and need to be reapplied.

A further disadvantage of conventional application methods is that theconcentration of bioactive ingredients resulting from a singleapplication of insecticide starts out well above the minimum levelnecessary for effectiveness, but decreases rapidly and within arelatively short period of time drops below the minimal effective levelnecessary to maintain a barrier.

To this end, a number of techniques for the controlled release ofchemicals such as insecticides have been developed in recent years.These methods employ polymer matrices and microcapsules to releaseinsecticide.

Cardarelli U.S. Pat. No. 4,400,374 discloses the use of polymer matricesgenerally made of polyethylene, polypropylene, ethylene vinyl acetate,polyamide, polystyrene, polyvinyl acetate, or polyurethane to controlthe release of insecticides such as the insecticide commerciallyavailable under the tradename Dursban. The polymer matrices disclosed inU.S. Pat. No. 4,400,374, incorporate porosigen and a porosity reducingagent which upon contact with soil moisture or an aqueous environmentdissolves the matrix.

Similarly, Cardarelli U.S. Pat. No. 4,405,360 relates to a polymerrelease matrix which can be composed of polyamide, polyurethane,polyethylene, polypropylene, polystyrenes and other polymers. Thecontrol release mechanism works in combination with a porosigen torelease a herbicide in a moist environment.

A disadvantage of the Cardarelli methods is the necessity of sufficientmoisture to dissolve the matrix. Periods of dryness, while extending thelife of the matrix, would result in a decrease in the insecticideconcentration thereby permitting access to the insects. In addition, thelongevity of the matrix is variable and dependent upon moisture content.

In addition, Wysong U.S. Pat. No. 4,435,383 teaches the use of acontrolled release mechanism for insecticides including carbamates,organothiophosphates, organophosphates, perchlorinated organics andsynthetic pyrethroids. The release mechanism comprises a hydrophobicbarrier monomer namely styrene and/or methyl styrene in combination witha monomer selected from one or more unsaturated mono- or di-carboxylicacids.

Another reference, Tocker U.S. Pat. No. 4,282,209 discusses a processfor the preparation of insecticide-polymer particles. The insecticide,methomyl, is used to control insects which attack a tobacco, cotton oragricultural crops. Methomyl is dissolved with polymers such aspolyamides, urethanes and epoxies to provide extended residualinsecticidal activity.

A second Tocker patent, U.S. Pat. No. 4,235,872, discloses the use ofslow-release insecticide microcapsules having a core of methomylsurrounded by a cover of allaromatic, uncrosslinked polyurea. In thearrangement disclosed in this patent, methomyl is used to protectvegetables, field crops and fruit crops.

A sixth reference, Young et al. U.S. Pat. No. 4,198,441, discloses theuse of insecticides such as Dursban in a controlled release matrixcomprising an organopolysiloxane, a hydrolyzable silane and ahydrolyzable organic titanium.

Additionally, Young et al. U.S. Pat. No. 4,160,335 discloses a mode ofdispersing insect control substances by applying stripes to sheets ofcellophane. The insect control substance which can include Dursban isplaced in a polymer as well.

Another method is described in an Australian patent AU-B-82443/91. Inthis patent, there is described two sheets of plastic drawn from supplyrolls. The upper face of the lower sheet and the lower face of the uppersheet are drawn past respective coating rollers which apply a coating ofpesticide (e.g. permethrin) in a volatile solvent to the faces of thesheets. The coated faces of the sheets are brought together by passingthem between compressive rollers. The coated and pressed sheets are laidunder building foundations, or placed around trees or plants to preventtermite attack. Disadvantages of this product and method include (1)severance of a layer permits rapid escape of the coating, and (2) thecoating is not integral to the sheets thereby permitting fasterdiffusion through the sheets and limiting the effective life.

Coated granules have a pesticide absorbed onto a matrix such as clay andthen coated with cross-linked resins which helps slow the release rate.Clay loses or releases pesticide over a short period of at most a fewweeks.

Although the prior art does disclose the use of an insecticideincorporated into a polymer matrix as controlled release agents, none ofthe references teach the creation and maintenance of a completelyeffective exclusion zone lasting several years or more. It is desirableto create a zone so as to prevent any contact between the wood structureand insects capable of damaging such structures. A reliable exclusionzone is necessary to protect wood structures for periods of timesubstantially greater than one year.

Therefore, in view of the above, it is an object of this invention toprovide a zone of insecticide to protect wooden structures. Such zoneconsisting of a long term low volatility barrier and a high volatilityshort term barrier to protect soil.

It is a further object of this invention to maintain an exclusion zonefor relatively great lengths of time of about 10 to 20 years.

SUMMARY OF THE INVENTION

The present invention is a wood pest barrier having a lifetime that iseffective over the life of the structure. The lifetime is achieved bybinding the pesticide within the polymer matrix thereby substantiallypreventing release of the pesticide from the polymer. Binding may beachieved by mixing the pesticide with a carrier as a bound friable mixprior to placing the bound friable mix within the polymer matrix.

The barrier may be supplemented with additional layer(s) including butnot limited to scrim, mesh, sheet, and combinations thereof. Theadditional layer(s) may contain a second pesticide that is the same ordifferent compared to the pesticide in the barrier. In addition, thesecond pesticide may be permitted to release from the additionallayer(s) for enhanced short term protection.

The barrier and/or additional layer(s) are made with a polymer selectedfrom the group consisting of thermoplastic polymers, thermoset polymers,elastomeric polymers and copolymers thereof. By incorporating theinsecticides into the polymers, the insecticides can be held or releasedat such a rate that they will continue to be effective as toxicants orrepellents for insects capable of damaging wood structures for aprolonged period of time while at the same time maintaining sufficientconcentrations within the barrier to prevent insect penetration throughthe barrier.

According to one aspect of this invention, there is provided apolymeric-carrier system wherein the pesticide is bound to the carrieras a bound friable mix. The sheeting with the bound friable mix is thenplaced near a wooden structure to provide a barrier that wood pests donot penetrate. An additional layer may provide means for a slow andrelatively constant release of the volatile insecticide in order tocreate a barrier zone beyond the barrier itself in the soil around awood structure. The polymers include thermoplastic polymers, thermosetpolymers, elastomeric polymers as well as copolymers thereof and theinsecticide comprises the family of insecticides known as pyrethrins.

According to another aspect of this invention, an exclusion zone iscreated by placing an extrusion near the wooden structure to beprotected. The extrusion has a polymeric delivery system capable ofcontrolled release of the insecticide. The carrier system maintains asteady and effective concentration of insecticide in the exclusion zonefor great lengths of time.

According to another aspect of this invention, a pellet comprising apolymer and insecticide is provided to create and maintain anequilibrium concentration of insecticide for ants, termites and otherwood boring insects in an exclusion zone for the wooden structure. Thepellet is placed near a wooden structure to treat the soil in order toshield the wooden structure from termites, ants and other boringinsects. The pellet can be placed near the structure by a variety ofmeans. Additionally, the pellet can be embedded in a board or evenincluded in a foam. In preferred embodiments the polymers includethermoplastic polymers, thermoset polymers, elastomeric polymers as wellas copolymers thereof and the insecticide are pyrethrins.

According to another aspect of this invention, an exclusion zone iscreated by injecting a hot melt polymeric mixture. The controlledrelease device comprises one or more pyrethrins and the polymer isselected from the group consisting of thermoplastic polymer, elastomericpolymers and copolymers thereof.

According to further aspects of the invention, temperature drivencontrolled release devices are used to provide the exclusion zones.

According to another aspect of this invention, the controlled releasedevice is used to fumigate structures.

It is desirable to place a barrier or create a zone so as to prevent anycontact between the wood structure and insects capable of damaging suchstructures. An exclusion zone is necessary to protect wood structuresfor extended periods of time.

In a further aspect of the present invention a high density polymerhaving a low volatility insecticide providing a low release rate ofinsecticide is combined with a low density (soft) polymer having a morevolatile insecticide to provide a reliable exclusion zone.

Therefore, in view of the above, it is an object of this invention toprovide a barrier of insecticide to protect wooden structures.

It is a further object of the present invention to provide a barrier andan exclusion zone having of a long term low volatility barrier and ahigh volatility short term barrier to protect adjacent soil.

It is a further object of this invention to maintain a barrier forrelatively great lengths of time or about 10 to 20 years.

The present invention, together with attendant objects and advantages,will be best understood with reference to the detailed description belowread in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a first embodiment of the invention, comprisingspun-bonded polymeric sheeting, and a physical melt-bonded mixture ofpolymer and insecticide, wherein the mixture of polymer and insecticideis bonded in spots to the polymeric sheeting.

FIG. 2 illustrates a second embodiment of the invention, comprisingspun-bonded polymeric sheeting, and a physical melt-bonded mixture ofpolymer and insecticide, wherein the mixture of polymer and insecticideis bonded in stripes to the polymeric sheeting.

FIG. 3 illustrates a first manner of using the embodiments of theinvention shown in FIGS. 1 and 2 and the exclusion zone created by therelease of insecticide.

FIG. 4 illustrates a second manner of using the first and secondembodiments of the invention to create an exclusion zone.

FIG. 5 illustrates a third manner of using the embodiments of theinvention shown in FIGS. 1 and 2 creating an exclusion zone.

FIG. 6 illustrates a third embodiment of the invention, in the form of acylindrical extrusion.

FIG. 7 illustrates a fourth embodiment of the invention, in the form ofa flat strip extrusion.

FIG. 8 illustrates a manner of creating an exclusion zone using theembodiment of the invention shown in FIG. 6.

FIG. 9 illustrates a manner of using the embodiment of the inventionshown in FIG. 7 to create an exclusion zone.

FIG. 10 illustrates another embodiment of the invention in the form ofpellets wherein the pellets are being inserted into the ground near awooden structure.

FIG. 11 illustrates a cross-sectional view of pellets placed on asurface.

FIG. 12 illustrates the application of pellets to a concrete structureutilizing foam.

FIG. 13 illustrates a cross-sectional view of a concrete foundationafter foam has been applied.

FIG. 14 illustrates pellets set on a board.

FIG. 15 illustrates a board containing pellets being applied to aconcrete foundation.

FIG. 16 illustrates a hot-melt injection.

FIG. 17 illustrates the spacing of the hot-melt injunction.

FIG. 18 illustrates a plug fumigating cement blocks.

FIG. 19 illustrates a mode of applying plugs to fumigate cement blocks.

FIG. 20 shows a layered apparatus of the present invention.

FIG. 21 shows repellency of Eastern subterranean termites.

FIG. 22 shows repellency of Formosan subterranean termites.

DETAILED DESCRIPTION

It has been found that there is a significant reduction of insectscapable of damaging wood structures when a barrier alone or incombination with an exclusion zone of insecticide is maintained forgreat lengths of time in the soil surrounding such structures. Anexclusion zone is a zone having a sufficient amount of chemical agent todeter fauna. In the present invention, the chemical agent is aninsecticide and the fauna are insects especially boring insects, forexample termites and ants. According to the present invention, theinsecticide is held in a barrier and/or is released from a controlledrelease device comprising a polymer matrix system will last for at least6 years.

A controlled release device refers to an apparatus that results incontrolled and sustained release of an bioactive chemical to its surfaceand from its surface into a surrounding medium, for example soil. Theapparatus provides a method for controlled release of the chemical intothe surrounding environment. The device releases insecticide at a highrate initially and a lower, steady rate thereafter. This release profileassures that the wooden object becomes protected in a relatively shortperiod of time and that, subsequent to reaching the minimum effectivelevel only the amount of insecticide necessary to replace the degradedinsecticide is released. This release profile diminishes potentialenvironmental and health problems of the treatment and reduces the costof the treatment. The apparatus release rate is dependent only upon theapparatus construction and is independent of external elements such aswater.

The controlled release device provides a near to mid-term solution byreleasing the insecticide into the soil at a desired rate to create azone having the “minimal effective level” of insecticide necessary toprevent insect intrusion. As used in this specification and the appendedclaims, the term “minimal effective level” is defined to mean the levelof insecticide needed in the zone to prevent insects from entering thezone, the specific level depends on the specific insect and the specificinsecticide. When placed adjacent to a foundation or below-gradestructural portion, the exclusion zone is created in the soil near theapparatus. When placed between a non-wood structural portion and anattached wood structural portion, the exclusion zone is created at theinterface between the non-wood structural portion and the attached woodstructural portion.

The insecticides used in preferred embodiments should be U.S.Environmental Protection Agency approved insecticides to kill or repeltermites, ants and other boring insects. The insecticide which ispresently preferred for use in the present invention are pyrethrins,including tefluthrin, lambdacyhalothrin, cyfluthrin and deltamethrin. Itwill, however, be recognized by those skilled in the art that othereffective insecticides such as isofenphos, fenvalerate, cypermethrin,permethrin and natural pyrethrin can also be used. These are availablefrom a number of commercial sources such as Dow, Mobay, ICI, Velsicoland FMC respectively. A combination of insecticides, or one or moreinsecticides in combination with other bioactive ingredients such asfungicides is also in accord with this invention.

A first controlled release embodiment of the invention, is illustratedin FIG. 1, utilizes a polymeric-carrier apparatus for the controlledrelease of insecticide to generate an exclusion zone. The embodimentcomprises spun-bonded polymeric sheeting 20, and a physical melt-bondedmixture of polymer and insecticide (shown as spots 21 in FIGS. 1 and3-5). The spun-bonded polymeric sheeting 20 can be either a woven ornon-woven textile or it can be a polymeric sheet. Such textiles can beobtained from a number of manufacturers such as Reemay, Exxon Fibers andPhillips Fibers. Preferably, the textile is woven or non-wovenpolypropylene.

The polymer in the melt-bonded mixture can comprise any number ofthermoplastic polymers, thermoset polymers, elastomeric polymers orcopolymers thereof. The selection of the polymers depends upon thedesired release rate, the compatibility of the polymer with insecticideand upon environmental conditions. By way of example and not intendingto limit the scope of this invention, the following polymers can beused: high density polyethylene, low density polyethylene, vinylacetate, urethane, polyester, santoprene, silicone, or neoprene.However, the preferred polymers are high density and low densitypolyethylene. Although the above-mentioned insecticides can be used forbest results, the insecticide should ideally comprise chlorpyrifos.

The mixture of polymer and insecticide may be placed on the spun-bondedpolymeric sheeting in spots. These spots should be spaced so as toadequately maintain the amount of insecticide above the minimaleffective level in an exclusion zone. The minimal effective level is theleast amount of insecticide needed in a zone so as to prevent intrusionby insects. Spots 21 in FIGS. 1 and 3-5 are preferably about 0.5 to 1.5centimeters in diameter, and about 0.5 to 1.5 centimeters in height. Thesize and shape of the spots will depend upon the user's preference andcan be tailored to the job contemplated by the buyer. The spots 21 canbe configured in rows with the spacing of the spots preferably beingfrom about 1.5 to 4 centimeters from adjacent spots. It will berecognized by those skilled in the art that other configurations ofspots can also be used depending on the particular application. Theinsecticide releasing polymeric sheet is placed near or around thewooden structure to create an exclusion zone by the controlled releaseof insecticide.

A second controlled release embodiment of the invention also utilizes apolymeric-carrier delivery system for the controlled release ofinsecticide comprising spun-bonded polymeric sheeting 20 and a physicalmelt-bonded mixture of polymer and insecticide. The polymeric sheeting20 as in the first embodiment can be either woven or non-wovenpolypropylene upon which is bonded the physical melt-bonded mixture(shown as stripes 22 in FIG. 2). Similarly, the polymers and insecticidedescribed above with respect to the first embodiment may also be used inthe embodiment described in this section.

The mixture of polymer and insecticide of the second embodiment mayalternatively be placed on spun-bonded polymeric sheeting using extrudersystems which provide stripes, e.g., as shown in FIG. 2. The stripes 22can be about 1 centimeter in height, and about 5 to 15 centimetersapart. Optimally the stripes should be placed about 10 centimetersapart. It is desirable that the stripes should be configured in such anarrangement so as to permit a steady state concentration of insecticidein the exclusion zone after an initial burst of insecticide. After thestripes are applied to the polymeric sheet, the sheet is placed on ornear the wooden structure to be protected from insects.

Binding filler and/or carriers may also be included in all of theembodiments of the invention. The inclusion of the binding filler and/orcarrier permits greater amounts of insecticide for a given release rateor permits a lower release rate for a given amount of pesticide. Thebinding carrier binds the pesticide. Binding carriers found to bind thepesticide include carbon based carriers for example carbon black,activated carbon and combinations thereof. It is believed that alumina,silicoaluminate, hydroxyapatite and combinations thereof may becomparable to carbon for binding bioactive chemicals.

When a carbon based carrier is utilized, the first step is to insuredryness of the carbon followed by mixing the insecticide in a liquidform with the carbon. Only sufficient carbon black (filler) is used toproduce a friable mixture. The term “friable” means substantially dry ornon-sticky flowable particles. Certain pesticides may have to be heatedto achieve a liquid form. The liquid insecticide adheres or binds to theextremely large surface area of the finely divided carbon black and themixture is cooled for incorporation in the polymer. Polymers which maybe used in a carbon application are a polyethylene, polypropylene,copolymers or blends of polyethylene and polypropylene, polybutylene,epoxy polymers, polyamides, acrylate-styrene-acrylonitrile, aromatic orunsaturated polyesters, polyurethanes, silicones, or any other suitablepolymers or copolymers thereof.

The carbon-insecticide mixture in the first and second embodiments (orjust insecticide, if carbon is not used) is then mixed with the polymer,preferably polyurethane, in either the molten, powder or liquid stage.Next this mixture is bonded to the polymeric sheeting. In the first andsecond embodiments of the invention, the polymer and insecticide aremelt-bonded to the polymeric sheeting.

Another mode of bonding the mixture of polymer and insecticide to thepolymeric sheeting is by “through-injection molding”, a technique whichis known in the art. In “through-injection molding”, molten material isinjected from a heated nozzle through a porous web and into a mold. Themolten material flows through the web under pressure and is solidifiedin the mold. While the molten material is being injected, the porous weballows air to escape, but it also retains the molten mass under pressureuntil it has cooled.

A different method of bonding the mixture of polymer and insecticide tothe polymeric sheeting is by placing a melted mixture of polymer andinsecticide on the spun-bonded polymeric sheeting. If the mixture ismelted, it must be allowed to cool, cure and solidify. As usedhereinafter, “a melted mixture of polymer and insecticide” is intendedto indicate that the polymer is either melted or already in the liquidstage. The insecticide may also be melted or contained in a slurrysolution, depending on its melting point. A “melted mixture of polymerand insecticide” can also contain carbon or other additives which do notmelt but flow with the melted polymer/insecticide mass.

The first and second embodiments of the invention should provide releaserates sufficient to maintain an effective insecticide concentration inthe exclusion zone to kill or repel insects but at sufficiently slowrates to maintain an effective concentration for an extended period oftime.

Overall, a preferred composition for the first and second embodiments ofthe invention comprises from about 70 to 95 parts by weight of carrierpolymer, from about 0 to 15 parts by weight of carbon, and from about 5to 30 parts by weight of insecticide. The design considerations of thecontrolled release devices vary according to such factors as userpreference and geographic conditions. The steady state release rate ofthe polymeric delivery system of these two embodiments after the initialburst of insecticide can be maintained for at least 6 years as a barrierto insects such as ants and termites. However, the equilibriumconcentration of this embodiment can easily be adjusted to meet thespecific needs of each user.

Optionally, the embodiments shown in FIGS. 1-5 may comprise apesticide-impervious sheet (not shown) such as a metallized foil. Themetallized foil or an extruded sheet of a polymer is laminated to oneside of the spun-bonded polymeric sheeting in order to direct the flowof insecticide.

A further embodiment of the present invention is a barrier of apest-impervious sheet wherein a bound friable mix of the bioactivechemical or pesticide with a carbon carrier is placed within a polymerand exhibits substantially no release of the bioactive chemical.Substantially no release is defined as a release rate less than 0.4μg/cm²/day, preferably less than 0.1 μg/cm²/day, and most preferablyless than 0.05 μg/cm²/day. This embodiment encompasses a release rate of0.0 or below detectable limits. In this embodiment, pests are deterredupon “sniffing” or “scratching” a polymer surface and detecting thepresence of the pest harmful bioactive chemical. Life time of thebarrier is much longer than a barrier with a higher release rate.Moreover, a flaw or tear in the polymer will be less prone to “leak”bioactive chemical. Hence, two or more layers of this embodiment may bepreferred to maintain a complete barrier. Multiple layers would permit atear or hole in one layer but a pest would not pass a second orsubsequent untorn layer. It may further be desirable to place aprotective layer, for example scrim, on one or both sides of a barrierlayer to avoid tearing.

Once made, the polymeric-carrier delivery systems of the first andsecond embodiments are placed near the structure desired to be protectedfrom insects. FIGS. 3-5 illustrate various applications of either thespotted or striped sheet embodiments of the invention. The FIG. 1configuration is shown in FIGS. 3-5, but it is understood that the FIG.2 configuration, or other configurations can work as well.

In FIG. 3, the polymeric-carrier delivery system 1 is placed under andalongside a concrete foundation 23 of a wooden structure 100 creating anexclusion zone 10 to protect the structure from termites, ants and otherboring insects.

In FIG. 4, the polymeric-carrier delivery system 2 is placed under astructural member 24, such as a porch, patio, sidewalk, or under abasement foundation beside the wooden structure 101 to provide anexclusion zone 10.

In FIG. 5, the polymeric-carrier delivery system 3 is placed over and onthe sides of the concrete foundation 23 of a wooden structure 102, butunder the wooden portion 25 of the structure to create an exclusionzone.

Another embodiment of the invention is illustrated in FIGS. 6 and 7.This embodiment pertains to extrusions, such as extruded flexiblecylinders 26 and extruded flexible flat strips 27 shown respectively inFIGS. 6 and 7. A wide variety of polymers which can be classified intofour broad subgroups can be utilized. The groups include thermoplasticpolymers, thermoset polymers, elastomeric polymers and copolymers of thethree groups named above. By way of example, some polymers which can beused from the four groups are: high density polyethylene, low densitypolyethylene, EVA, vinyl acetate, urethane, polyester, santoprene,silicone, neoprene and polyisoprene. The preferred insecticide ischlorpyrifos although the insecticides described above can be used. Afiller may also be added.

Cylinders preferably have a size ranging from about 5 to 15 millimetersin diameter, but most preferably about 10 millimeters in diameter forthe optimal steady state delivery of insecticide into the exclusionzone. Flat strips should preferably have a thickness of from about 1 to6 millimeters and a width of from about 5 to 15 millimeters. It,however, should be noted that both cylinders and flat strips can bedesigned to meet the varying conditions encountered by user.

Overall, in order to maintain an equilibrium concentration of pesticidein the exclusion zone for an extended period of time, the composition ofthis embodiment of the invention, should comprise from about 70 to about95 parts by weight of polymer, from about 0 to about 30 parts weight ofcarbon, and from about 5 to about 30 parts by weight of pesticide. Thecomposition of the extrusion can, however, be tailored to the specificneeds of the user. It is estimated that the exclusion zone can bemaintained for at least 6 years for a cylinder and likewise for flatstrips.

The extrusions can be positioned in a variety of positions to createexclusion zones. FIG. 8 illustrates a manner of using the extrusionshown in FIG. 6. One or more flexible cylinders 26 are placed betweenthe concrete foundation 23′ and the wooden portion 25′ of the structure.The flexible cylinders 26 release insecticide at a controlled rate tocreate an exclusion zone. An advantage of this configuration is thatflexible cylinders 26 can be placed under a structure that has alreadybeen built. Similarly, in a manner not shown, the flexible cylinders canbe placed vertically into the ground as opposed to horizontally. As willbe recognized by those skilled in the art, the extrusions may have othersuitable shapes and be placed in any suitable position depending uponthe particular use contemplated.

FIG. 9 illustrates a manner of using the flexible flat strip extrusionshown in FIG. 7. One or more flexible flat strips 27 create an exclusionzone by being placed between or alongside the concrete foundation 23″and the wooden portion 25″ of the structure. The flexible flat strips 27can also be placed vertically alongside a wall in an embodiment notillustrated in the drawings. Again, any suitable placement of the flatstrips is considered as being within the scope of the invention.

The controlled release of insecticide can also be conveniently achievedby using pellets as illustrated in the embodiments shown in FIGS. 10-13.The pellet 13 comprises polymer, insecticide and preferably alsoincludes a filler. Various polymers can be used in this embodiment. Theycan comprise polymers of four subgroups consisting of thermoplasticpolymers, thermoset polymers, elastomeric polymers and copolymersthereof. Polymer selection from these four subgroups depends upon designconsiderations with the preferable polymer being either high densitypolyethylene or low density polyethylene. In turn, the insecticidepreferable comprises tefluthrin, but the following insecticides can alsobe used: isofenphos, fenvalerate, cypermethrin, permethrin and otherpyrethrins. For optimal results, a carrier such as carbon, can also beincorporated into the mixture.

The pellet 31 releases insecticide at a controlled rate for an extendedperiod of time in order to establish an exclusion zone. The compositionfor such a pellet needed for the maintenance of a zone in the soil isfrom about 70 to about 95 parts by weight of polymer, from about 0 toabout 30 parts by weight of carbon black, and from about 5 to about 30parts by weight of insecticide. Ultimately, the compositions of thepellet depend upon user preference.

The pellets can be any convenient size depending upon the intended use,such as 1 to 25 millimeters in diameter (or width and thickness, ifrectangular) by 2 to 20 centimeters or more in length. Furthermore, inorder to fit specific user needs, the dimension of the pellets and theconcentrations of the insecticide can easily be adjusted. However, anexclusion zone can be maintained for at least 6 years.

Additionally, pellets 31 have the advantage that they can beconveniently placed most anywhere. The pellets of this embodiment of theinvention are shown in FIG. 10. A pellet 31 is inserted near a woodenstructure 25. The pellets as illustrated in FIG. 10 can be placed undera cement foundation 23′″ or they can be placed directly under the woodstructure (not illustrated) so as to permit the creation of a zone 10surrounding the wooden structure 25′″ to exclude insects capable ofdamaging such structures. FIG. 11 shows a cross-sectional view ofpellets 31 inserted on a surface 40.

Pellets are easily applied to a wide variety of uses. FIG. 12illustrates pellets sprayed 50 onto a concrete structure surface 40.FIG. 15 illustrates treating a surface by placing pellets 33 onpreformed boards 300.

Pellets 32 are applied onto a surface 40 such as soil or concrete via afoam 41 as illustrated in FIG. 13. The pellets are first incorporatedinto a foam in a manner known in the art. The foam 41 containing thefine pellets is then sprayed 50 as illustrated onto the surface 41 via amotorized sprayer 70 in FIG. 12 so as to provide a protective coatingfor the surface. The pellets 32 then release the insecticide to create aprotective barrier in the soil to protect the wood from harmful insects.For best results, the foam 50 is comprised of polyurethane. It is alsopossible to use silicone, polyester, or polyvinyl acetate. The pellets32 can vary in size depending upon the foam thickness and the desiredconcentration of insecticide in the exclusion zone. The thickness of thefoam to be applied to a surface can vary according to user's preference.The exclusion zone can be maintained for at least 6 years. In additionto being used as a carrier for insecticide, the foam also cures cementand acts as an insulator.

A preformed board with embedded pellets 33 can also be utilized as anembodiment of this invention as illustrated in FIG. 14. This board 300can be made of any type of material which can suitably hold the pellets33. Preferably, the board is comprised of styrofoam which is registeredas a Dow trademark. The board can be applied in any variety of fashionsand can also work as an insulating device. One manner of application isillustrated in FIG. 15, where the board 300 with pellets 33 is placedabove a concrete surface 42. The embedded pellets are regularly spacedwith the spacing being specified by the devised amount of insecticide.

In another embodiment as shown in FIGS. 16 and 17, the controlledrelease device comprising the polymer matrix and insecticide can beapplied via a hot melt. This embodiment is designed to meet the needs ofstructures already in place. As stated above, the polymer matrix cancomprise any of the four above-named polymer groups. Similarly, any ofthe above-named insecticides can be utilized. However, it is preferableto use high or low density polyethylene with either a pyrethrin.Although tailored to the user, the concentrations of the varioussubstances in the hot-melt application should range from about 70 toabout 95 for the polymer, from about 5 to about 30 for the insecticideand from about 0 to about 30 for filler/carrier for optimal results.

FIG. 16 shows hot melt 50 being injected by a syringe 400 into theground near a concrete foundation 43. The concrete structure 43 supportsa wooden structure 250. FIG. 17 shows the spacing between the hot melt50 which has already been injected into the ground.

In another embodiment, FIGS. 18 and 19 illustrate the use of insecticideto fumigate a structure 500. By injecting or placing the controlledrelease device in or near a structure which can be fumigated, theinsecticide release from the controlled release device can vaporizethereby fumigating the structure. FIG. 18 illustrates the use of plugs34 to fumigate a structure 500 made of building blocks 502. Similarly,FIG. 19 illustrates a mode of applying the controlled release device byusing a drill 800 to bore a hole 700 into a cement slab 900. Onceinserted, the plug is able to fumigate the structure.

CURRENTLY PREFERRED EMBODIMENT

The currently preferred embodiment of the apparatus of the presentinvention as shown in FIG. 20 combines a first polymer 200 of medium orhigh density polymer having a low vapor pressure insecticide with asecond polymer 202 of low density having a more volatile, vis highervapor pressure, insecticide. High, medium and low density are terms wellknown in the polymer art referring to the degree of cross linking withina polymer. High vapor pressure is defined as vapor pressure in excess ofabout 1 millipascal and preferably ranges from about 10 millipascals toabout 100 millipascals. Low vapor pressure is defined as less than 1millipascal and preferably ranges from about 0.05 millipascals to about0.5 millipascals. The first polymer 200 preferably has a thickness inthe range from about {fraction (1/32)} to ⅛ inch. The low vapor pressureinsecticide, is preferably permethrin or lambdacyhalothrin. Thepreferred material of the first polymer 200 is selected from amongpolyurethane, high density polyethylene and polypropylene. The secondpolymer 202 is placed adjacent to and, preferably attached to the firstpolymer 200. It is preferred that the first polymer 200 be water andradon impermeable. Hence, the first polymer 200 is preferably a sheetthat may be a film or spun bonded. According to the present invention,the first polymer 200 may be in two sub-parts with one sub-part 204 apermeable medium or high density polymer containing the low vaporpressure insecticide and another sub-part 206 an impermeable layerhaving no insecticide within. The impermeable layer has an advantage forhandling of preventing or reducing exposure/contact of the installerwith the bioactive chemical. The impermeable layer may be, for exampleMylar, saran or saranax.

The second polymer 202 is a low density polymer, preferably an ethylenevinyl acetate, a low density polyethylene or blend thereof. The morevolatile or higher vapor pressure insecticide placed within the secondpolymer is preferably a synthetic pyrethroid, for example tefluthrin.

The second polymer 202 may be in the form of pellets as previouslydescribed and the first and second polymers deployed with the firstpolymer under a sill plate on a foundation and the second polymerscattered in the soil adjacent the foundation. More preferably, thesecond polymer 202 is in the form of an open mesh, either woven ornon-woven as shown. Mesh openings may range from touching but not sealedto about 1 to four inches square and ribs 208 having a cross sectionwidth of from about 1 mil to about ⅛ inch. A scrim that can be made frompolyethylene, polypropylene, or polyester maybe used as the mesh. With afirst polymer 200 sheet and a second polymer 202 open mesh, theapparatus of the combination of the fist and second polymers 200, 202 ispreferably placed below grade. The first polymer sheet 200 is placedadjacent the second polymer 202 open mesh with the first polymer 200sheet in contact or near a foundation 43 and between the foundation andthe second polymer 202 open mesh. The mesh material may absorb bioactivechemical and contribute to the reservoir of bioactive material.

In operation, the first polymer 200 maintains a physical/chemicalbarrier against insect intrusion. However, because of the slow releaseof the first polymer 200, very little insecticide is released that wouldbe available to create an exclusion zone within about the first yearafter installation. In addition, it is impossible to install a defectfree barrier because of penetrations, for example electrical andplumbing, and because of punctures or tears during construction.Accordingly, the second polymer 202 is deployed to create exclusionzones within a few days of installation thereby preventing insect accessthrough the imperfections of the first polymer 200. The first polymer200, therefore has three functions: insect barrier, vapor/moisturebarrier, and radon barrier. The first polymer 200 is designed to last atleast 10 years and preferably up to and in excess of 20 years. Thesecond polymer 202 is designed to last at least 5 years and preferablyup to about 10 years. By the time that the second polymer 202 isdepleted and no longer effective against insects, the first polymer 200will have developed a concentration of released insecticide sufficientto maintain the exclusion zone.

The following examples are provided by way of explanation. As such,these examples are not viewed as limiting the scope of the invention asdefined by the appended claims.

EXAMPLE 1

Experiments were conducted to determine the release rate ofchlorpyrifos. Loading rates for the insecticide were either 5 wt % or 10wt %, depending on polymer. Release rates were determined for alldevices at 50° C.

Polymers evaluated included low melt polyethylene, polyurethane, twoepoxies, silicone rubber, and a low melt polyethylene high in waxes toreduce thermal decomposition of the chlorpyrifos. Studies indicated thatexcessive thermal decomposition of the chlorpyrifos occurred attemperatures in excess of approximately 240° C.; thus, polymer selectionwas restricted to formulations not requiring excessive heat processing.

Table 1 provides a summary of the results from these studies. Overall,polymer compatibility with chlorpyrifos did not appear to present aproblem with the loading rates employed. There was some loss of physicalintegrity of the polyurethane polymer employed, however, the otherpolymer systems exhibited no visible degradation at 50° C. Release ratesranged from 10 μg/cm²/da for the silicone rubber, to 0.3 μg/cm²/da forEpoxy B.

Using the data provided in Table 1, an estimated product longevity canbe approximated. Assuming a device wt. of 0.5 g, with 10% load, then 50mg of chlorpyrifos is available for release. Thus, for a polymer systemhaving an area of 4 cm², and a release rate of 1 μg/cm²/da, there issufficient insecticide to last 30 years at elevated temperature. Thesecalculations indicate that a variety of insecticidal products arepossible.

TABLE 1 Polymer Formulations and Release Rates for Candidate SystemsEmploying Chlorpyrifos. Polymer Chlorpyrifos Release Rate Class Content(%) (μg/cm²/da)^(a) Polyurethane  5  2.1 ± 1.4^(b) Epoxy A  5 <0.1Silicone  5 10.3 ± 3.5 Urethane 10  1.0 ± 0.3 Epoxy B 10  0.3 ± 0.1 PE +Wax 10  1.9 ± 0.3 ^(a)Release rates performed at 50° C. ^(b)Materialexhibited excessive cracking at elevated temperature

EXAMPLE 2

Studies were also conducted with similar polymer systems as in Example 1but with 80% pure pyrethrin. Release rates at 40° C. are provided inTable 2.

TABLE 2 Polymer Formulations and Release Rates for Candidate SystemsEmploying Pyrethrin I. Polymer Pyrethrin I Release Rate Class Content(%) (μg/cm²/da)^(a) Epoxy A 10  0.5 ± 0.2 Silicone 10 21.2 ± 5.4Urethane 10 15.7 ± 7.1 Epoxy B 10  0.2 ± 0.1 ^(a)Release rates performedat 40° C.

The release rates were highest for urethane and silicone and lowest forthe epoxies. Substantial variability in release rates were encounteredand appropriate binders will need to be evaluated.

From the data in Table 2, simple calculations can be performed todetermine the possible life of the insecticide systems. As stated inExample 1, there are many variables which can alter the lifetime of anexclusion zone.

EXAMPLE 3

Controlled release devices were made and tested to obtain their releaserates. All thermoplastic polymers were formulated with 10 percentpesticide, 3 or 7 percent carbon black to absorb liquid pesticide and 83to 87 percent by weight of polymer and injection molded into thin sheetsabout ⅛ inch thick. Specifically, devices made from thermoplasticpolymers and deltamethrin and lambdacyhalothrin contained 3 percent ofcarbon black. The devices made from the remaining pesticides andthermoplastic polymers contained 7 percent of carbon black.

The devices made from S-113 urethane (a thermoset polymer) were madefrom a polymer mix containing 60% S-113, 40% castor oil and 5% of TIPAcatalyst by weight. The polymer mix comprised 90% of the total weight ofthe device. The pesticide, deltamethrin, comprised the remaining 10% ofthe device. No carbon black was used in this device. Thepolymer/pesticide mixture was cast into a ⅛ inch thick sheet and heatedat about 60° C. for about 40 to 60 minutes to cure the cast sheet.

One inch squares were then cut from the thin sheets that were injectionmolded or cast and the squares were tested for release rates. Thefollowing release rates were obtained:

Pesticide Polymer Release Rate Deltamethrin S-113 urethane 25.2μg/cm²/day Aromatic 80A 16.8 μg/cm²/day Pellethane 2102-80A 8.8μg/cm²/day Pellethane 2102-55D 8.0 μg/cm²/day Alipmtic PS-49-100 7.2μg/cm²/day Cypermethrin polyurethane 3100 0.4 μg/cm²/day polyurethane2200 0.7 μg/cm²/day EVA 763 27.3 μg/cm²/day Polyethylene MA778-000 4.6μg/cm²/day Lambdacyhalothrin polyurethane 3100 0.7 μg/cm²/daypolyurethane 2200 2.0 μg/cm²/day EVA 763 20.6 μg/cm²/day PolyethyleneMA778-000 5.2 μg/cm²/day Tefluthrin polyurethane 3100 6.4 μg/cm²/dayPolyurethane 2200 25.0 μg/cm²/day EVA 763 40.4 μg/cm²/day PolyethyleneMA778-000 27.0 μg/cm²/day Permethrin polyurethane 3100 1.4 μg/cm²/daypolyurethane 2200 1.3 μg/cm²/day EVA 763 28.5 μg/cm²/day PolyethyleneMA778-000 4.0 μg/cm²/day

EXAMPLE 4

An experiment was conducted to determine the effect of lambdacyhalothrin(pyrethroid) concentration and insecticide/polymer combination onrelease rate of insecticide from the polymer. The data are summarized inTable 4.

TABLE 4 Release Rate for Polymer/Pyrethroid Concentration Combinations.Pyrethroid Release Rate Polymer Conc. (wt %) (mg/cm²/day) EthylvinylAcetate (EVA) 1 0.3 5 2.2 10  2.5 Polyurethane 1 0.9 5 4.4 10  8.3Polyurethane/EVA (50/50) 1 2.6 5 7.2 10  9.1

EXAMPLE 5

An experiment was conducted to determine the effectiveness of theexclusion zone against termites. Two species of termites were selectedfor the tests: Eastern subterranean termite because it is the mostcommon, and Formosan subterranean termite because it is the mostaggressive.

Test cells were assembled with glass containers. Wood shavings wereplaced in the bottom of the containers. Insecticide impregnated polymerwas placed over the wood chips in a manner that no path or openingexisted from above the impregnated polymer to the wood chips. A nutrientfree auger was placed above the impregnated polymer. The surface of theauger was the zero datum and the impregnated polymer was mounted at adistance of 5 cm below the surface of the auger. Termites were placed onthe surface of the auger and their progress through the auger toward theimpregnated polymer noted each day.

The impregnated polymer combinations are shown in Table 5a.

TABLE 5a Release Rate for 10 wt % Pyrethroid Release Rate PolymerPyrethroid (mg/cm²/day) Ethylvinyl acetate Permethrin 3.9 Ethylvinylacetate Tefluthrin 4.3 Ethylvinyl acetate Tefluthrin 3.2 (2 wt % fattyacid) Polyethylene Permethrin 1.4 Polyethylene Tefluthrin 2.2Polyethylene Tefluthrin 2.0 (2 wt % fatty acid)

Controls having no pyrethroid in a polymer barrier were also used.Results are shown in FIG. 21 and FIG. 22. In all controls, the termitesate through the polymer and obtained access to the wood chips. The rateof access through ethylvinyl acetate was slower than for polyethylene.For all impregnated polymers, there was no penetration. Because theFormosan subterranean termites are so aggressive, they came closer tothe impregnated polymer than the less aggressive Eastern subterraneantermites. In fact, the polyethylene with permethrin suffered mandiblemarks from the Formosan termites, but no holes or penetration. Afterabout 12-14 days, even the Formosan termites were discouraged by therelease of insecticide and retreated from impregnated polymer.

EXAMPLE 6

An experiment was conducted to demonstrate the effect of a bindingcarrier on release rate. The active chemicals were tefluthrin andlambdacyhalothrin in an amount of 5 wt %, the binding carrier was carbonblack in amounts of 0 wt % and 10 wt %, with the balance high densitypolyethylene (MA 778-000). Release rates were measured at 6 weeks afterfabrication wherein samples were wiped weekly to remove surfaceaccumulation of released active chemical.

Results are shown in Table 6.

TABLE 6 Release Rates for 0 wt % and 10 wt % Carbon Black Active CarbonBlack Release Rate Chemical (wt %) (μg/cm²/day) tefluthrin  0 3.13tefluthrin 10 0.71 lambdacyhalothrin  0 1.78 lambdacyhalothrin 10 0.81lambdacyhalothrin 20 0.61

CLOSURE

From the foregoing description one skilled in the art can easilyascertain the essential characteristics of this invention and withoutdepartment from the spirit and scope of the invention thereof can makechanges and modifications of the invention in order to adapt it to thevarious usages and conditions. It is intended that the scope of theinvention be defined by the following claims including all equivalentswhich are intended to define this invention.

We claim:
 1. A multi-layer barrier for preventing a wood pest fromaccessing a wooden structure, the barrier comprising: (a) a first layercomprising a first polymer, a liquid pesticide, and a carrier, whereinsaid first polymer is selected from the group consisting of high densitypolyethylene, low density polyethylene, ethylene vinyl acetate, vinylacetate, urethane, polyester, a thermoplastic elastomer, silicone,neoprene, polyethylene, polyurethane, polypropylene, polybutylene, epoxypolymers, polyamides, acrylate styrene-acrylonitrile, aromaticpolyesters, unsaturated polyesters, polyisoprene, and combinationsthereof, said first polymer forming a polymer matrix, the pesticidebound to the carrier to form a pesticide-carrier mixture, the polymermatrix being formed by mixing the first polymer and thepesticide-carrier mixture to form a mixture, melting the mixture, andsolidifying the mixture to form the polymer matrix, thepesticide-carrier mixture bound within the polymer matrix, saidpesticide is selected from the group consisting of isofenphos,fenvalerate, cypermethrin, permethrin, tefluthrin, lambdacyhalothrin,cyfluthrin, deltamethrin, and combinations thereof, and wherein thecarrier is selected from the group consisting of carbon black, activatedcarbon, alumina, silicoaluminate, hydroxyapatite and combinationsthereof; and (b) a second layer located adjacent the first layer, saidsecond layer of a second polymer, said second layer being impermeablesuch that the pesticide is substantially not released from the barrierbut it released from the barrier at a rate which is less than 0.4μg/cm²/day such that the wood pest is prevented from breaching thebarrier.
 2. The barrier of claim 1, wherein the pesticide is releasedfrom the barrier at a rate which is less than 0.1 μg/cm²/day.
 3. Thebarrier of claim 1, wherein the pesticide is released from the barrierat a rate which is less than 0.05 μg/cm²/day.
 4. The barrier of claim 1,wherein the first polymer comprises low density polyethylene and thepesticide comprises lambdacyhalothrin.
 5. The barrier of claim 1,wherein the pesticide comprises lambdacyhalothrin.
 6. The barrier ofclaim 1, wherein the amount of the pesticide is at least 1 wt % of thepolymer matrix.
 7. The barrier of claim 5, wherein the amount of thepesticide is at least 5 wt % of the polymer matrix.
 8. The barrier ofclaim 1, wherein the first polymer is selected from the group consistingof polyurethane, high density polyethylene, and polypropylene and thepesticide is selected from the group consisting of permethrin,lambdacyhalothrin, and combinations thereof.
 9. The barrier of claim 1,wherein the first polymer is a low density polymer.
 10. The barrier ofclaim 1, wherein the first polymer comprises low density polyethylene.11. The barrier of claim 1, wherein the carrier is carbon black.
 12. Thebarrier of claim 1, wherein the first layer is in the form of a sheet,strip or pellet.
 13. The barrier of claim 1, wherein the second layer isa sheet made from polyethylene terephthalate film, a copolymer ofvinylidene chloride and vinyl chloride, or a coextruded multi-layeredbarrier film.
 14. The barrier of claim 1, wherein the first polymer is amedium or high density polymer and the pesticide is a low volatilitypesticide.
 15. The barrier of claim 1, further comprising one or moreadditional layers selected from a scrim, mesh, sheet combinationsthereof.
 16. The barrier of claim 15, wherein the at least one saidadditional layer is located adjacent the first layer and comprises athird polymer and a second pesticide, wherein the third polymer forms asecond polymer matrix and the second pesticide is bound within thesecond polymer matrix.
 17. The barrier of claim 15, wherein the at leastone said additional layer is attached to the first layer and comprises athird polymer and a second pesticide, wherein the third polymer forms asecond polymer matrix and the second pesticide is bound within thesecond polymer matrix.
 18. The barrier of claim 15, wherein the at leastone said additional layer is in the form of a mesh.
 19. The barrier ofclaim 16, wherein the third polymer is a low density polymer and thesecond pesticide is a high volatility pesticide.
 20. The barrier ofclaim 1, wherein the barrier further comprises at least one strength andpuncture resistant layer.
 21. The barrier of claim 20, wherein the atleast one said strength and puncture resistant layer is made of apolymeric scrim.
 22. The barrier of claim 1, wherein the pesticide isbound to the carrier to form a bound friable mix.
 23. The barrier ofclaim 1, wherein the barrier further comprises a metallized layer.
 24. Amulti-layer barrier for preventing a wood pest from accessing a woodenstructure comprising: (a) a first layer comprising a first polymer, aliquid pesticide, and a carrier, the pesticide is selected from thegroup consisting of isofenphos, fenvalerate, cypermethrin permethrin,tefluthrin, lambdacyhalothrin, cyfluthrin, deltamethrin and combinationsthereof, the first polymer forming a first polymer matrix, the liquidpesticide bound to the carrier to form a pesticide-carrier mixture, thepesticide-carrier mixture bound within the polymer matrix, the polymermatrix being formed by mixing the first polymer and thepesticide-carrier mixture to form a mixture, melting the mixture, andsolidifying the mixture to form the polymer matrix, wherein said firstpolymer is selected from the group consisting of high densitypolyethylene, low density polyethylene, ethylene vinyl acetate, vinylacetate, urethane, polyester, a thermoplastic elastomer, silicone,neoprene, polyethylene, polyurethane, polypropylene, polybutylene, epoxypolymers, polyamides, acrylate-styrene-acrylonitrile, aromaticpolyesters, unsaturated polyesters, polyisoprene, and combinationsthereof, and wherein the carrier is selected from the group consistingof carbon black, activated carbon, alumina, silicoaluminate,hydroxyapatite and combinations thereof; (b) a second layer locatedadjacent the first layer, said second layer made of a second polymer,said second layer being impermeable such that the pesticide issubstantially not released from the barrier but is released from thebarrier at a rate which is less than 0.4 μg/cm²/day such that the woodpest is prevented from breaching the barrier, and (c) a third layerlocated on the opposite side of the first layer which is made of astrength and puncture resistant material.
 25. The barrier of claim 24,wherein the pesticide is released from the barrier at a rate which isless than 0.1 μg/cm²/day.
 26. The barrier of claim 24, wherein thepesticide is released from the barrier at a rate which is less than 0.05μg/cm²/day.
 27. The barrier of claim 24, wherein the carrier is carbonblack.
 28. The barrier of claim 24, wherein the first polymer of thefirst layer comprises low density polyethylene and the pesticide of thefirst layer comprises lambdacyhalothrin.
 29. The barrier of claim 24,wherein the second layer is made from polyethylene terephthalate film, acopolymer of vinylidene chloride and vinyl chloride, or a coextrudedmulti-layered barrier film.
 30. The barrier of claim 24, wherein thethird layer is made of a polymeric scrim.
 31. The barrier of claim 24,wherein the barrier further comprises a fourth layer located between thefirst and the third layer, wherein the fourth layer comprises a thirdpolymer and a second pesticide, said third polymer forms a secondpolymer matrix, said second pesticide bound within the second polymermatrix.
 32. The barrier of claim 31, wherein the barrier furthercomprises a fifth layer, wherein said layer is made of metallized foil.